When comparing targeting precision between DBS in parkinsonian patients and OCD patients, an unexpected deviation from the planned targets was discovered in OCD patients (Nuttin et al., 2013). The objective of this trial is to investigate whether the use of a micro-electrode assisted technique improves targeting precision in DBS at the BNST.

Inclusion Criteria:

• Diagnosis of OCD following the diagnostic and statistical manual of mental disorders-fourth edition (DSM-IV) criteria for OCD (300.3).
• Failure of documented trials of pharmacotherapy, following an appropriate treatment algorithm for OCD.
• Failure of documented trial of cognitive and behavioural therapy
• Duration of illness: min. 5 year
• Y-BOCS (Yale-Brown Obsessive Compulsive Scale) at least 30/40.
• Age: 20-65 year

Exclusion Criteria:

• DSM-IV diagnosis on axis 2 of severe personality disorder in cluster A or B, especially in the case of heightened risk for acting-out behavior.
• DSM-IV diagnosis on axis 3 of organic brain pathology or significant abnormalities on MRI.
• Present or past history of psychotic symptoms.
• Present substance abuse, or instable remission of substance abuses (i.e. no substance abuse during the last 12 months).
• Any disorder affecting cognitive functioning, other than motor tics and Gilles de la Tourette's Syndrome
• Mental retardation. A minimum threshold of cognitive skills is needed for adequate reporting on questionnaires and evaluation, and for technical handling of the instruments in a later faze.